First Limiting Amino Acid and Gross Protein Value of Yeast and Bacteria grown on Methanol and Ethanol for Growing Chicks

Abstract

The first limiting amino acid in two samples of yeast grown on methanol, a sample of yeast grown on ethanol, two samples of bacteria grown on methanol, and two samples of brewer's yeast as a kind of reference was determined, and gross protein value of these samples with supplementation of the first limiting amino acid was assayed biologically with starting chicks.Amino acid content of experimental diets containing 20% of crude protein, of which 12% was derived from one of the samples, was calculated from amino acid composition of the samples determined chemically. Comparing with requirements of essential amino acids for starting chicks, those deficient in the diets were picked up, and supplemented to the diets. Growth response of chicks fed the diets revealed that the first limiting amino acid in all of the samples except Yeast K grown on methanol is sulfur-containing amino acids.Gross protein value of all the samples except Yeast K was improved significantly by supplementation of DL-methionine at a level of 1-2% of crude protein in the sample. Except a sample of brewer's yeast, Yeast K without supplemental DL-methionine and other samples with DL-methionine had excellent gross protein value over 80.